For an optical disc, there is a Compact Disc (hereinafter referred to as CD) adapted so that, e.g., audio signals are recorded as pit trains in a spiral form from the inner circumference toward the outer circumference on one side surface of the disc. The CD player or the disc player serves to irradiate laser beams onto the pit trains by using the optical pick-up while allowing such a CD to undergo rotational drive at a constant linear velocity to detect changes of light quantity of a reflected light thereof to reproduce the audio signals.
On the other hand, as a medium for recording audio signals, there is a record disc of the analog system (type) adapted so that sound grooves corresponding to stresses of sounds are provided in a spiral form from the outer circumference to the inner circumference of the disc of vinyl resin to thereby record respective audio signals as an analog signal. The record player of the analog system serves to rotate the record disc mounted on a turn table rotating at a constant angular velocity to trace these sound grooves by means of the reproduction needle to detect vibrations of the reproduction needle thus to reproduce audio signals.
Meanwhile, a style of rendition called scratch using a record disc and a record player as described above is known. In accordance with such rendition, e.g., in the field of dance music, a disc jockey repeats several times such an operation to control, by hand, rotation of the record disc rotating on the turn table to rotate the record disc by several centimeters in a backward rotational direction, and then to subsequently rotate it in the forward rotational direction to rotate it in the backward rotational direction for a second time.
Sound reproduced by this scratch essentially consists of noise generated as the result of the fact that the reproduction needle traces the sound grooves in a direction opposite to the reproduction direction when the record disc is rotated in a backward direction, and short phrase when the record disc is rotated in a forward direction and is returned therefrom. As the result of the fact that combinations of noises and short phrases as described above are repeated several times, peculiar rhythms are generated. Rhythms produced by this scratch constitute important element which is indispensable for the specific dance music.
Meanwhile, the above-described CD is chucked on the CD player. When the pick-up is placed (located) at the innermost circumference, the CD is rotated at about 600 revolutions per minute (r.p.m.), and when the pick-up is placed (located) at the outermost circumference, the CD is rotated at about 200 r.p.m. This number of revolutions corresponds to a value about 18 times to 6 times greater than the number of revolutions of the ordinary record player of the analog system.
It is impossible to carry out the scratch rendition by controlling rotation by hand, similarly to the record disc, with respect to the CD rotating at a high speed in the state chucked on the CD player as described above. However, also in the CD player, there is strong demand for realization or performance of scratch rendition.
In view of the above, an object of this invention is to provide an optical disc reproducing apparatus and an optical disc reproducing method which can obtain similar effects as in the scratch rendition of the record disc.